Data

Perinatal Indicator: Infant Mortality

Definition: the number of infants who die in the first year of life, for every 1000 live births.

Why Does This Matter? Infant mortality is one of the most important indicators of the health of a nation, as it reflects such factors as maternal health, quality of, and access to medical care, socioeconomic conditions, and public health practices. The U.S. has one of the highest infant mortality rates of all developed nations. In 2004, the U.S. ranked 29th in the world in infant mortality, tied with Slovakia and Poland. The U.S.’s ranking has steadily fallen from 12th in 1960, to 23rd in 1990, and to 29th in 2004. The five leading causes of infant death in the U.S., accounting for 54% of the total in 2005, are birth defects (20%); preterm birth and/or low birth weight (17%); Sudden Infant Death Syndrome (8%); newborns affected by maternal complications of pregnancy (6%); and newborns affected by complications of placenta, cord and membranes (4%).

Birth defects are often associated with prematurity, low birthweight, SIDS, and complications during pregnancy. Infants are at greater risk of death if their mothers have certain conditions or diseases when they become pregnant, including diabetes, infections, hypertension, obesity, and poor nutritional status. Lifestyle factors such as smoking, drug and alcohol abuse, and stress can also increase the risk.

Preterm birth is a key risk factor for infant death. Preterm infants accounted for 68.6% of all infant deaths in 2005, up from 65.6% in 2000. In 2000 and 2005, very preterm infants accounted for only 2% of births, but over 50% of all infant deaths. The infant mortality rate for very preterm infants was 183.24 infant deaths per 1,000 live births in 2005, not significantly different from the rate in 2000 (180.94), halting a long decline. From 2000 to 2005, the percentage of preterm births in the U.S. increased 9%, from 11.6% to 12.7%. Late preterm births had the most dramatic rise, at 11%. In 2005, the infant mortality rate for late preterm births was three times that for term births. For multiple births, the infant mortality rate was 31.5 per 1,000, more than five times the rate for single births.

In 2005, multiples accounted for 3% of all live births, but 15% of all infant deaths in the U.S. [see perinatal indicator 5: Multiple Births, for more information.] In 2005, about two-thirds of all infant deaths occurred during the neonatal period (from birth to 27 days old). The neonatal mortality rate was 4.54 deaths per 1,000 live births, essentially unchanged from the previous year. However, the postneonatal (between 28 days and 1 year) rate of 2.32, was 3% higher than the 2004 rate.

Infant mortality rates vary with maternal age; the highest rate is for infants of teenage mothers (10.28) followed by those of mothers over the age of 39 (7.85). The lowest rates are for infants of mothers in their late twenties and early thirties. Infant mortality rates were higher for first births than for second births, and then increased with subsequent births. Infants of married mothers had a mortality rate of 5.25 per 1000 live births, 45% lower than the rate for infants of unmarried mothers. Since 1980, California’s infant mortality rate has remained lower than the U.S. rate. In California, in 2004, the rate was 5.2, the same as for 2003.

Number of Infant Deaths (Birth– 1 Years Old) Los Angeles County (2005)

Source: HealthyCity.org, Advanced Mapping, accessed February 12, 2010, Data Request: Geography, Los Angeles County Health - Disease and Mortality » Deaths by Age » Age less than 1 year. Number of deaths at less than 1 year of age.